1. Field of the Invention
The invention relates to a method and an apparatus for controlling a position of a built-in camera installed in an equipment, such as a monitoring camera, for the purpose of appropriately taking a photograph of an object, and more particularly to a method of automatically controlling a position of a built-in camera, and an apparatus for implementing the method.
2. Description of the Related Art
A monitoring system using a camera for photographing a particular portion of an object located at a predetermined location has been disclosed in Japanese Unexamined Patent Publication No. 62-140563.
FIG. 1 is a block diagram illustrating the major parts of the monitoring system described in the Publication.
When a detector 16 detects that there is a person standing in front of a main unit of an automatic cash dispenser, a control circuit 29 actuates a switch 30 in such a manner that a scanning drive circuit 24 is electrically connected to a servo circuit 23. At the same time, the scanning drive circuit 24 is activated by the control circuit 29. The servo circuit 23 drives a motor 22 in synchronization with output signals transmitted from the scanning drive circuit 24.
A mirror 21 is rotated by the motor 22. The mirror 21 is provided with a detector 25. When the detector 25 is above a face 20 of the person standing in front of the cash dispenser, the detector 25 transmits an increasing output signal as the detector 25 approaches the face 20. In a range where a distance between the detector 25 and the face 20 remains substantially constant, the detector 25 transmits an approximately constant output signal. As the detector 25 is spaced away from the face 20, the output signal decreases gradually.
The detector 25 transmits an output signal to an angle setting circuit 27 through a detector circuit 26. The angle setting circuit 27 computes such an angle of inclination of the mirror 21 that an image of the face 20 is projected exactly onto a picture-taking plane of a camera 12 through the mirror 21 and a fixed mirror 28, on the basis of the output signals transmitted from the detector 25. As a result, the mirror 21 is inclined by an appropriate angle to thereby ensure that a photograph of the face can be surely taken.
The monitoring system disclosed in the above-mentioned Publication thus ensures that a predetermined portion of a person, such as a face thereof, can be photographed reliably in dependence on a height of the person, even though people have different heights.
However, the above-mentioned monitoring system has problems as follows.
A first problem of the aforementioned conventional monitor system is that since the monitor system is not provided with a function of changing a position of the monitor camera 12, it is impossible to directly change the viewing angle of the monitor camera 12. Consequently, mirrors such as the mirror 21 and the fixed mirror 28 have to be used, resulting in that the monitor system cannot avoid having a complicated structure.
A second problem of the monitor system is that the camera 12 cannot directly take a photograph of an object, because the camera 12 is fixed, and thus, has to adjust an angle of the mirror 21 to thereby take a photograph of an object which is reflected in the mirror 21. The use of the movable mirror 21 causes a problem that an optical system required for the monitor system cannot avoid having a complicated structure, and has to have a high accuracy.
A third problem concerned with the monitor system is that complicated computation which would take much time is necessary to be conducted before taking a photograph of an object, because the camera 12 has to be scanned to detect a position of the object, followed by computation of the position, and then, the mirror 21 is driven by a computed angle. Furthermore, high accuracy is required for controlling an optical system, and there has to be conducted a complicated control for driving the mirror 21.
A fourth problem of the monitor system is as follows. The camera 12 has to be scanned again to adjust an orientation of the camera 12 so that the camera 12 is directed toward a detected position of an object. Hence, if a direction in which the camera 12 can take a photograph most suitably varies, the camera 12 has to be adjusted quickly to follow such a varying direction. However, such adjustment is quite difficult or almost impossible.